I liked @MauriceMizrahi’s explanation!
I found another explanation:
The Midrash quotes the pasuk in Tehillim 104:2 as a proof that Hashem surrounded Himself with light,”עֹֽטֶה־א֭וֹר כַּשַּׂלְמָ֑ה נוֹטֶ֥ה שָׁ֝מַ֗יִם כַּיְרִיעָֽה, “wrapped in a robe of light; You spread the heavens like a tent cloth.” In the Tikunei Zohar 55b:8 (https://www.sefaria.org/Midrash_Tanchuma%2C_Vayakhel.6.1?lang=bi&p2=Psalms.104.2&lang2=bi&w2=Tikkunei%20Zohar&lang3=en) it metions, אִיהִי טַלִּית דְּקוּדְשָׁא בְּרִיךְ הוּא, וּבָהּ אִתְעַטֵּף קוּדְשָׁא בְּרִיךְ הוּא, that this refers to the Talit of Hashem, and with it He wraps Himself.
Practically this is what it could mean: The Gemera in Rosh Hashanah 17b says, ״וַיַּעֲבוֹר ה׳ עַל פָּנָיו וַיִּקְרָא״. אָמַר רַבִּי יוֹחָנָן: אִלְמָלֵא מִקְרָא כָּתוּב, אִי אֶפְשָׁר לְאוֹמְרוֹ. מְלַמֵּד שֶׁנִּתְעַטֵּף הַקָּדוֹשׁ בָּרוּךְ הוּא כִּשְׁלִיחַ צִבּוּר, וְהֶרְאָה לוֹ לְמֹשֶׁה סֵדֶר תְּפִלָּה. אָמַר לוֹ: כׇּל זְמַן שֶׁיִּשְׂרָאֵל חוֹטְאִין — יַעֲשׂוּ לְפָנַי כַּסֵּדֶר הַזֶּה וַאֲנִי מוֹחֵל לָהֶם. “The verse states: “And the Lord passed by before him, and proclaimed” (Exodus 34:6). Rabbi Yoḥanan said: Were it not explicitly written in the verse, it would be impossible to say this, as it would be insulting to God’s honor. The verse teaches that the Holy One, Blessed be He, wrapped Himself in a prayer shawl like a prayer leader and showed Moses the structure of the order of the prayer. He said to him: Whenever the Jewish people sin, let them act before Me in accordance with this order. Let the prayer leader wrap himself in a prayer shawl and publicly recite the thirteen attributes of mercy, and I will forgive them.”
The Mahrasha (ibid) says, נתעטף הקב"ה באותו טלית לבנה שנתעטף בברייתו של עולם שעליו נאמר עוטה אור כשלמה שמבהיק מסוף העולם ועד סופו. Hashem wrapped Himself in the same tallit that he wrapped when he created the world, of that which it says שמבהיק מסוף העולם ועד סופו, that it glows from one end of the world to another. So maybe (I'm not sure if its the same light) this light which goes from one end of the world to another represents the אור הגנוז, since the Gemera in Chagigah 12a says:
כִּדְרַבִּי אֶלְעָזָר. דְּאָמַר רַבִּי אֶלְעָזָר: אוֹר שֶׁבָּרָא הַקָּדוֹשׁ בָּרוּךְ הוּא בְּיוֹם רִאשׁוֹן, אָדָם צוֹפֶה בּוֹ מִסּוֹף הָעוֹלָם וְעַד סוֹפוֹ. כֵּיוָן שֶׁנִּסְתַּכֵּל הַקָּדוֹשׁ בָּרוּךְ הוּא בְּדוֹר הַמַּבּוּל וּבְדוֹר הַפְּלַגָּה וְרָאָה שֶׁמַּעֲשֵׂיהֶם מְקוּלְקָלִים — עָמַד וּגְנָזוֹ מֵהֶן, שֶׁנֶּאֱמַר: ״וְיִמָּנַע מֵרְשָׁעִים אוֹרָם״. “Rabbi Elazar said: The light that the Holy One, Blessed be He, created on the first day was not that of the sun but a different kind of light, through which man could observe from one end of the world to the other. But when the Holy One, Blessed be He, looked upon the generation of the Flood and the generation of the Dispersion and saw that their ways were corrupt and that they might misuse this light for evil, He arose and concealed it from them, as it is stated: “And from the wicked their light is withheld” (Job 38:15).”
This would show that this light is therefore the Talit which represents the Or Haganuz (or some type of light that goes from one end to another).